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From "David Smiley (JIRA)" <>
Subject [jira] [Updated] (LUCENE-1736) general improvements
Date Mon, 06 Jun 2011 21:13:00 GMT


David Smiley updated LUCENE-1736:

    Attachment: LUCENE-1736_DateTools_improvements.patch

This is an updated patch.
* The former "DateFormats" class was used as a value in a ThreadLocal which isn't a good idea
as it hampers class reloading.
* Improvements to a switch statement to benefit from fall-through.
* Removed a pointless conversion to Calendar in timeToString()
* Moved functionality to Resolution enum, and used arrays of Resolutions indexed by format
length instead of large if-else or switch blocks for format & parse. The ramification
is 48 fewer lines of code.

> general improvements
> -----------------------------------
>                 Key: LUCENE-1736
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/index
>    Affects Versions: 2.9
>            Reporter: David Smiley
>            Priority: Minor
>             Fix For: 4.0
>         Attachments: LUCENE-1736_DateTools_improvements.patch, cleanerDateTools.patch
> Applying the attached patch shows the improvements to that I think should
be done. All logic that does anything at all is moved to instance methods of the inner class
Resolution. I argue this is more object-oriented.
> 1. In cases where Resolution is an argument to the method, I can simply invoke the appropriate
call on the Resolution object. Formerly there was a big branch if/else.
> 2. Instead of "synchronized" being used seemingly everywhere, synchronized is used to
sync on the object that is not threadsafe, be it a DateFormat or Calendar instance.
> 3. Since different DateFormat and Calendar instances are created per-Resolution, there
is now less lock contention since threads using different resolutions will not use the same
> 4. The old implementation of timeToString rounded the time before formatting it. That's
unnecessary since the format only includes the resolution desired.
> 5. round() now uses a switch statement that benefits from fall-through (no break).
> Another debatable improvement that could be made is putting the resolution instances
into an array indexed by format length. This would mean I could remove the switch in lookupResolutionByLength()
and avoid the length constants there. Maybe that would be a bit too over-engineered when the
switch is fine.

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